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Aim: Evaluation of inhibitory effect of emulsifiers on pancreatic trypsin and α-chymotrypsin., Methods: The inhibitory effect of Cremophor EL, Cremophor RH 40, Brij O10, Tween 20, polyethylene glycol 8000, polyethylene glycol 400, Carbitol, Pemulen TR-1, Pemulen TR-2, Carbopol Ultrez 20 and Carbopol Ultrez 21 on pancreatic trypsin and α-chymotrypsin was tested. BAEE (Nα-Benzoyl-l-arginine ethyl ester), BTEE (N-Benzoyl-l-tyrosine ethyl ester), casein and insulin were used as substrates for trypsin and α-chymotrypsin. SEDDS containing Pemulen TR-2 were developed, loaded with insulin-DMPG (dimyristoylphosphatidylglycerol) complex, characterized and tested regarding the protective effect towards the proteolytic degradation of insulin., Results: Cremophor EL, Cremophor RH 40, Brij O10, Tween 20, polyethylene glycol 8000, polyethylene glycol 400, Carbitol did not show any inhibitory effect towards trypsin and α-chymotrypsin, whereas Pemulen TR-1, Pemulen TR-2, Carbopol Ultrez 20 and Carbopol Ultrez 21 inhibited the enzymes in a concentration dependent manner. Moreover, Pemulen and Carbopol Ultrez emulsifiers exhibited comparable inhibitory properties (p>0.05). The incorporation of 0.34% w/w of Pemulen TR-2 in SEDDS decreased the degradation rate of the loaded insulin-DMPG complex compared to the blank formulation (p<0.05)., Conclusion: The present study revealed that commonly used emulsifiers in SEDDS do not have inhibitory properties on the proteolytic activity of trypsin and α-chymotrypsin. Moreover, it was demonstrated that the incorporation of emulsifiers with inhibitory properties towards trypsin and α-chymotrypsin in SEDDS play a minor role in the protection of embedded drugs from enzymatic degradation., (Copyright © 2017 Elsevier B.V. All rights reserved.)